High resolution adjustable transducer employing an auxiliary transducer



Apnl 7, 1970 B. SCOTT 5 5 HIGH RESOLUTION ADJUSTABLE TRANSDUCER EMPLOYING AN AUXILIARY TRANSDUCER Filed Oct. 25, 19 67 I fl v in 1 N VENT O R [arifuz B. 560 it United States Patent HIGH RESOLUTION ADJUSTABLE TRANSDUCER EMPLOYING AN AUXILIARY TRANSDUCER Larkin B. Scott, Fort Worth, Tex., assignor to The Perkin- Elmer Corporation, Norwalk, Conn., a corporation of New York Filed Oct. 23, 1967, Ser. No. 677,398 Int. Cl. Gf 3/00, 5/00, 7/00 U.S. Cl. 32343.5 7 Claims ABSTRACT OF THE DISCLOSURE This invention relates to signal transducers for use in electrical apparatus. The invention relates more particularly to an AC transducer adapted for providing an output voltage resolved to a relatively small fraction of an input voltage.

In one form of voltage transducing apparatus, an AC voltage (E is applied between input terminals of a continuous multiturn winding and an output voltage (E is derived at one or more taps on the winding. The output voltage is resolved to a desired fraction l/N or multiple of the input voltage where N is equal to the number of turns on the winding. For example, a transducer having a 1,000-turn winding employing a tap physically connected to a single turn will provide an output voltage resolved to l/N, i.e., to .001 of the input voltage or any given theoretical output voltage can be actually achieved to the nearest part in 1,000 with a maximum error of 2.0005. The transducer resolution is therefore referred to as 1:.0005. When (E has a value of 10 volts for example, the output voltage (E for a 1,000-turn winding can be resolved to $005 volts.

At times it is desirable to provide a transducer having a relatively higher degree of tap resolution. For example, it may be desirable to provide an output voltage resolved to 1200001 of the input voltage. This resolution can be accomplished by providing a winding having 50,000 turns. However, a winding arrangement with this large number of turns is impractical in view of the increased size and cost of manufacture of such a transducer.

Accordingly, it is an object of this invention to provide an improved voltage transducer.

Another object of the invention is to provide a voltage transducer adapted for providing an output voltage resolved to a relatively high degree of accuracy.

A known form of precision AC transducer comprises an autotransformer having a carefully fabricated winding and a plurality of winding taps located thereon. The transducer also includes a shaft-driven switching and interpolating means for deriving an output signal having an amplitude either at a particular tap on the winding or at positions on the transformer winding which lie intermediate the taps. Precision transducers of this type are described and claimed in U.S. Patents 2,843,822 and 3,027,510 which are assigned to the assignee of the present invention.

Patented Apr. 7, 1970 Precision AC autotransformer transducers are noted for a relatively high degree of conformity to a desired input-output signal relationship. This relationship may be linear or nonlinear. In general, the turns of the winding are positioned uniformly about a toroidal form and a desired input-output functional relationship is established by positioning the taps at properly selected number of turns on the winding. While in a linear transducer the winding taps will generally be spaced with an equal number of turns per section between taps for an equal increment of drive shaft angle, the number of turns per section between taps for equal shaft increments in a nonlinear transducer is not equal. The attainment of a desired high degree of resolution in a nonlinear transducer is thereby rendered substantially diflicult.

Another object of the invention is to provide an improved form of nonlinear precision transducer.

A further object of the invention is to provide a nonlinear precision transducer of the type described wherein a relatively high degree of resolution is attained at moderate cost and with moderate physical size of the transducer.

In accordance with features of the present invention, an electrical transducer includes a first continuous multiturn winding having a pair of input terminals between which an input voltage is applied. A second continuous multiturn winding is coupled across a plurality of turns of the first winding. The transducer includes an electrical contactmember. A tap voltage is established at the contact member 'by a conductive element which is coupled between a point on the first winding and the contact member and which is inductively coupled to the second winding. The degree of inductive coupling is selected to provide a desired additive or subtractive voltage increment. Through this arrangement, the tapping of the first winding is effectively resolved to a relatively high degree.

These and other objects and features of the invention will become apparent with reference to the following specifications and drawings wherein:

FIGURE 1 is a schematic circuit diagram of a precision AC transducer constructed in accordance with features of this invention; and,

FIGURE 2 is an elevation View, partly cut away and partly in section, illustrating the physical arrangement of the precision AC transducer of FIGURE 1.

Referring now to FIGURE 1, the transducer is shown to include a first continuous multiturn winding 10 formed about a body 12 of ferromagnetic material. An input voltage is applied between an input terminal 14 and a reference terminal 16 of the winding. A plurality of conductive elements 18-32 comprising Wire leads are provided for intercoupling positions 34-48 spaced along the winding 10 with associated contact members 50-64. As indicated hereinafter the contact members comprise commutator segments formed on a commutator 66.

In accordance with a feature of the present invention, an auxiliary transducer comprising a second continuous multiturn primary winding 68 is provided and is coupled across a plurality of turns of the first winding 10. The winding 68 is shown connected to the winding 10 at points 70 and 72. The winding 68 is formed about a body 74 of ferromagnetic material. At least a one of the conductive elements 18-32 is inductively coupled to the winding 68 and functions as a secondary winding. In FIGURE 1, elements 20, 24, and 26 are shown inductively coupled to this winding. The number of turns on the elements 20, 24, and 26 are selected to provide a desired additive or subtractive voltage increment to the voltage established on these elements at the winding tap points 36, 40, and 42. The windings of the conductive elements 20 and 2-4 are shown polarized for providing an additive increment while the winding of the element 26 is shown polarized for providing a substractive increment.

A means for progressively coupling the voltages at the contact members 50-64 to an output terminal 76 comprises a resistive interpolating means including resistances 78, 80, and 82. Wiper contact means comprising wiper contacts 84, 86, and 88 couple these resistances in sequence to successively positioned contact members and a wiper contact 90 driven in synchronism with the wiper contacts 84, '86, and 88 derives a voltage from a one of these resistances and couples this voltage to the terminal 76.

The transducer arrangement illustrated in FIGURE 1 is advantageous in that a relatively small number of turns is required on the first winding in order to provide a relatively high degree of resolution. For example, the winding 10 may comprise 1,000 turns which as indicated hereinbefore may be tapped with a resolution of i-.0005 of the input voltage. The second winding '68 is Wound with 500 turns, for example, and is coupled across a known number of turns of the winding 10 and is thereby excited by a portion such as .01 of the input voltage. To provide a .01 excitation, the winding 68 is coupled across 10 turns of the 1,000 turn winding 10 at the taps 70 and 72. The tapping resolution of the tap locations 36, 40, and 42 is effectively increased by the inductive coupling to the winding 68. A one-turn coupling provided by the conductive element 20 in the exemplary transducer would provide an additive voltage to that established at the tap 36 of .00002 per turn. The effective tapping resolution is thereby extended to 100001. For a winding 10 of fixed number of turns, the desired resolution and contact segment voltage for a particular application is established by the number of turns of winding 10 across which the winding 68 is coupled and the turns ratio between winding 68 and a conductive segment.

The physical arrangement of the transducer of FIGURE 1 is indicated generally in FIGURE 2. Elements in FIGURE 2 performing functions similar to elements in FIGURE 1 bear the same reference numerals. The continuous multiturn Winding 10 is formed about a toroidal core of ferromagnetic material 12 which is mounted in a lower portion of a transducer casing 92. The second Winding 68 is formed about a toroidal core of ferromagnetic material 74 which is supported at an intermediate position within the casing. Conductive elements coupling wire leads extend from the tap points on winding 10 through a support plate 94 and are connected to contact members of the commutator disc 66 positioned on a stationary internallytoothed gear 95 in an upper portion of the casing. The contact members extend radially and are circumferentially spaced about the disc. One or more of the conductive elements extend from the winding 10 and are wound about the core 74. As indicated hereinbefore, the conductive element includes one or more turns formed about the core in accordance with the desired tap voltage. Corresponding leads will extend from this core 74 to an associated contact member on commutator disc 66.

The interpolating resistances 78, '80, and 82 of FIGURE 1 comprise an annular wire-wound resistor 96 which is tapped at three equally-spaced points along its body. A dish 98 of insulating material supports the resistor and is mounted and secured to a planetary gear 100 by an insulating spacer member 102. The contacts 84, 86, and 88 are secured to a lower surface of the dish 98 and are each connected to a tap point on the resistor 96. An eccentric cam 104 is keyed to and driven by a rotatable drive shaft 106 and causes rotation of the gear 100 in mesh with the stationary gear 95. A collar 108 is keyed to the drive shaft and rotates therewith. The interpolating resistance wiper contact 90 is secured to a lower surface of the collar 108 and rotates along the annular resistor 96 in electrical contact therewith. A stationary wiper contact 110 is mounted in the upper casing by a support member 112 and is conductively coupled to the output terminal 76. The wiper contact 110 contacts a slip ring on the uppersurface of the collar 108 which is conductively coupled to the wiper 90. The resistive segments of the resistor 96 are thereby conductively coupled to the output terminal 76 as the shaft 106 is rotated.

The drive arrangement for the interpolating means as described is a planetary-gear, speed reduction arrangement. In this drive arrangement, the stationary gear includes a number of gear teeth equal to the number of contact members 5064. The rotatable planetary gear 100, which supports and rotates the wire Wound resistor 96, has one less gear tooth than the stationary gear 95. Rotation of the drive shaft causes the cam eccentric to drive the planetary gear 100, and, because of the one gear tooth difference, a counterrotation of the planetary gear a distance equivalent to the angular spacing of the contact members on the commutator disc 66 occurs with each shaft revolution. The resistive elements 78, 80, and 82 are thereby progressively coupled to successively positioned contact members and each of these resistive elements is traversed by the wiper contact 90.

An improved precision AC transducer has thus been described which is advantageous in that it effectively increases the resolution of the transducer without substantially increasing the physical dimensions of the transducer or the cost of fabrication thereof.

I claim:

1. In an electrical transducer including a first continuous multiturn winding having a pair of input terminals between which an input voltage is applied, an arrangement for deriving an output voltage from the transducer comprising:

an auxiliary transducer having a primary winding coupled across a number N of turns less than all of the turns of the first winding for establishing across said primary winding a voltage having an amplitude less than the amplitude of the input voltage;

an electrical contact member for said electrical transducer;

a secondary winding for said auxiliary transducer conductively coupled between a point on said first winding and said contact member, said primary and secondary windings having a turns ratio for inductively establishing across said secondary Winding a voltage having an amplitude equal to or less than a voltage existing between immediately successively positioned turns of said first winding.

2. In an electrical transducer including a first continuous multiturn winding having a pair of input terminals between which an input voltage is applied, an arrangement for deriving an output voltage from the transducer comp-rising:

a second continuous multiturn winding coupled across a plurality of turns less than all of the turns of the first winding for establishing across said second winding a voltage having an amplitude less than the amplitude of the input voltage;

an electrical contact member for said transducer;

a conductive element coupled between a point on said first winding and said contact member and inductively coupled to said second winding, said second winding and said conductive element inductively coupled for inductively establishing a voltage across said conductive element having an amplitude equal to or less than a voltage existing between immediately successively positioned turns of the said first winding.

3. The transducer of claim 2 wherein said first and second windings are positioned about first and second cores of ferromagnetic material and said conductive element is connected to said first winding and to said contact member and a portion thereof is wound about said core in a manner for providing inductive coupling with said second winding.

4. In a precision electrical transducer including a first continuous multiturn winding having a pair of input terminals between which an input voltage is applied, an arrangement for deriving from said first winding a voltage which is a portion of the input voltage and of a magnitude intermediate that established between successively positioned turns on said first winding comprising:

a second continuous multiturn winding coupled across a plurality of turns less than all of the turns of said first winding for establishing across said second winding a voltage having an amplitude less than the amplitude of the input voltage;

an electrical contact member for said transducer; I a conductive element coupled between said first winding at a point electrically intermediate said input terminals and said contact member and inductively coupled to said second winding, said second winding and said conductive element inductively intercoupled for establishing across said conductive element a voltage having an amplitude equal to or less than a voltage existing between immediately successively positioned turns of said first winding.

In a precision electrical transducer an arrangement for tapping portions of a voltage applied to a winding thereof comprising:

between points on said first winding electrically intermediate said input terminals and associated ones of said contact members, said conductive element and second winding inductively intercoupled for establishing across said element a voltage having an amplitude equal to or less than a voltage existing between immediately successive turns of said "first winding;

at least one of said conductive elements formed about said second core of ferromagnetic material to thereby provide inductive coupling between said element and said second continuous winding; an output terminal for said transducer; and, means for progressively coupling successively positioned contact members to said output terminals. 6. The transducer of claim 4 wherein said first and second windings are formed about associated toroidallyshaped cores of ferromagnetic material.

7. The transducer of claim 5 wherein said conductive elements comprise wire leads.

I References Cited UNITED STATES PATENTS 3,114,100 12/1963 Michaelis 323 3,129,382 4/1964 Scott 323-435 3,179,876 4/1965 Henman 32345 3,200,325 10/ 1965 Takeda 32343.5 3,223,919 12/1965 Langham 32343.5

LEE T. HIX, Primary Examiner G. GOLDBERG, Assistant Examiner US. Cl. X.R. 

